Imidazolinone compounds, for instance, those described in U.S. Pat. No. 4,798,619 and U.S. Pat. No. 5,334,576, are highly potent, broad spectrum, environmentally benign, herbicidal agents. In general, the herbicidal activity of the R-isomer is approximately twice that of the racemic imidazolinone compound. A process to prepare chiral imidazolinones via the resolved optically active 2-amino-2,3-dimethylbutyramide enantiomers and a process to prepare said aminoamide enantiomers are described in U.S. Pat. No. 4,683,324. However, the chiral imdazolinone compounds prepared therein require 3 separate process steps. Szczepanski and Durr describe a 2 step process to prepare racemic imdazolinone herbicides via the reaction of a racemic 2-aminoalkane carboxamide and a suitably substituted pyridine-2,3-dicarboxylate in U.S. Pat. No. 4,758,667. However, no reference or guidance to chiral imidazolinone preparation is described therein.
Accordingly, it is an object of this invention to provide a process to prepare essentially enantiomerically pure imidazolinone herbicidal agents directly from (R)2-amino-2,3-dimethylbutyramide in a simple manner and good yield and with substantially complete retention of optical purity.